Thursday, May 26, 2011

Hospital – acquired Infection

It is infection acquired while staying in hospital . It meets the following criteria :-

Not found on admission .

Temporally associated with admission or a procedure at a health care facility .

It was not incubating at admission and may be related to a previous procedure or admission to same or other health care – facility e.g HIV acquired from previous blood transfusion .

Routes of infection : -

Self infection (auto genous infection) .

Cross – infection .

Environmental infection

-Dust.

-Bed linen

-Air .

-Moist solutions may be contaminated Pseudomonas

Klebsiella

Factors which promote hospital acquired infection : -

Impaired general host defencas of the patient .

Impaired local host defences of the patient .e.g injury of skin barrier .

Presence of hospital pathogen which are endemic epidermidis . Increasing problem is associated with MRSA strepto . pneumonia is the next common gram positive assoiated with lower respiratory tract infection .

Types of hospital infection : -

The three most frequent types : -

Urinary tract infection .

Wound infection .

Lower respiratory tract infection .

Other types of less common infections : -

Bed sores and varicose ulcer infection

Alimentary tract infection .

All severe bacterial infections lead to septicaemia .

Organisms causing Hospital acquired infection : -

In many hospital but also each hospital has specific endemic or epidemic strains of particular types of organism in certain areas .

In hospitals with large specific units e.g oncology , special care baby units opportunists organisms as well as the common pathogens are likely to cause problem

Pathogens causing hospital acquired infections include

Conventional pathogen e.g strepto-pyogenes .

Conditional pathogen e.g Bacteroides .

Opportunists pathogen e.gPneumocystis carinii .

The most common organisms are staph. aureus and staph.epidermidis

-Gram Negative bacilli such as : -

E.coli is the most prequent single bacterial species associated with hospital acquired infection .

klebsiella , proteus species and Pseudomonas are also common cause .

- Fungal and viral infection are only ocassionaly acquired in hospital .

- Protozoa are rare .

Laboratory diagnosis Of Hospital – acquired Infections :

Samples collected from the patient includes Blood culture , sputum, tracheostomy wound swabs and other samples. Perform cultured before antibiotics therapies and judged accurately if the isolate is just contamination or already a true pathogen .

Samples from the environment includes all equipments in the ICU and from antiseptic solutions according to the place of environmental assay.

Typing of the isolated organisms from both patients, environment and personnel by the following typing methods :

Bio typing

Sero typing

Phage typing

Bacteriocine typing

DNA finger printing

1- Hospital – acquired urinary tract infections

The most common type of hospital infection (about 25%)

The source auto- genous from patient's own faecal flora or from the environment (urinals , wash bowl) .

Colonization of the patient's large intestine by hospital resistant strains of Gram – negative bacilli occurs when the patient stays in hospital more than few days or when patient take antibiotics .

E.coli is the most common pathogen especially resistant strains to sulfonamides and ampicillin other pathogens such as klebsiella aerogenes, Enterococcus spp. (Vancomycin resistant) and Pseudomonas are common .

Ocassionally candida and serratia marscenes may cause such infection .

Patients with impaired immune system may become infected wit T.B and Nocardia asteroids , salmonella spp. Or Papoviruses .

- Infected operation wounds , the operation site may be infected at time of surgery e.g incision of an abscess .

2) Surgical team:

- Skill of surgeon

- Good aseptic techniques

- Carriage of staph. aureus .

3) Age and general condition of the patient .

Persistence of local structural abnormal .

Ward factors post operatively

Complication of wound Infections : -

Delayed wound healing

Failure of graft .

Infections of bones , joints , peritoneal cavity .

Septiceamia

Types of hospital acquired wound infections include : -

Ward infection

Theatre infection

(How to differentiate ?)

Prevention of theatre infection : -

Protective of theatre clothing .

Gloves for the hands after chlorhexidine antiseptic solution

Movements of staff should be reduced to a minimum .

Very clean theatre with good managing of the air direction around the operative table .

Disifect the skin of the patient and many use preoperative baths with hexachlorophene or chlorhexidine detergents .

Prevention of wards infections : -

Isolation rooms for wards should be available for patients infected with MRSA or with severe wound infections especially in high risk surgery e.g cardio thoracic orthopaedic , neuro surgical units and ICU .

It is very common to find high rates of infections in intensive care units.

Samples collected from the patient includes Blood culture , sputum, tracheostomy wound swabs and other samples. Perform cultured before antibiotics therapies and judged accurately if the isolate is just contamination or already a true pathogen .

Samples from the environment includes all equipments in the ICU and from antiseptic solutions .

Preventive measures are the same as before and the measures for the equipments include : -

Adequate cleaning of the equipment in between patients

Heating water in the ventilator to 50oC every day .

Use of autoclavable ventilator or decontaminate it with ethylene or formaldehyde gas .

Precautions should be taken in the lab. To prevent infections to workers .

All staff with regular contact with blood should have anti HBS with titre > (10 lu/L)

Precautions to prevent viral hepatitis : -

Isolate the patients (stool / urine / needle isolation)

Take blood samples with gloves

Transport to the lab in sealed plastic bags.

Samples are put in upright position in non leaking screw caps containers

Samples and requests should be labeled ashepatitis risk .

Take care of samples from suspected patients .

Accidental prick to staff should be reported to senior staff , take hyper immune globulin with 24-48 hours and vaccinate if HBS antibodies is negative .

Wearing of two gloves , waterproof apron and goggles together with many other precautions are necessary when surgery is carried out on patients with hepatitis B. (universal precautions) .

Staff members positive for HBsAg or e antigen should not work in dialysis unit , oncology , surgery or transplant unit .

3)AIDS :

Blood and blood products should be screened for HIV 1/2.

Universal precautions against blood – borne viruses should be taken when blood or blood staining splashing are anticipated as risk .

Post exposure drug prophylaxis is recommended for staff sustaining a sharp injury from a patient or HIV .

Policies for Control of Hospital –acquired Infections

Each hospital has many procedures and policies which attempt to reduce the chances of hospital infection occurring , but the extent to which these policies are effectively carried out on a day to a day basis varies greatly between different hospitals or different areas in the hospital .

Procedures for control Include : -

Sterilization and disinfection of contaminated items .

Disposal of infected rubbish or linen .

Aseptic techniques in the operating theatre

Procedures carried in wards such as changing of wound dressings , urinary catheterization and setting up of an intravenousdrip .